With a strike against the Trump Taj Mahal casino about to enter its fourth week and no end in sight, Atlantic City's main casino workers union turned up the heat Thursday, surrounding the massive gambling hall with hundreds of picketers, some traveling hundreds of miles to support the walkout.  Local 54 of the Unite Here union held a rally and march around the casino with a crowd it predicted would reach 1,000 people.  Pickets from unions in Baltimore, Washington, New Haven, Pittsburgh, Philadelphia and New York were among the protesters.  The union walked off the job on July 1.  The Taj Mahal casino remains open.